Besides hotelscombined.com and kayak.com, are here any other multi-site search engines that people use to find LNF submission rates?
Have you not read post #1 in this thread???
It says:
Originally Posted by
imverge
Since many people are posting requests for help in finding a Look No Further Rate on this thread: Post Rate Guarantee Success!!
http://www.flyertalk.com/forum/marri...successes.html
**PLEASE DO NOT POST ANY COMPARISON SITES AS MARRIOTT IS MONITORING THIS THREAD**
PLEASE JUST POST THE CITY AND DATES YOU ARE LOOKING FOR 
We cannot compile a public list because of the above. Posting a (less-obvious) site here may just lead to fewer LNFs being possible in the future!!!
And, at any rate, different third-party sites work for different places and/or different hotels (even in the same area). What you should do is monitor the other thread of successful LNFs:
http://www.flyertalk.com/forum/marri...successes.html
and when you see that someone did a successful LNF at a property that you're interested in (or at least in a city that you're interested in), and you find you can't duplicate that with the third-party sites you already know about, then PM the person who posted the successful LNF and ask if they don't mind telling you which site they used.
Too many people LNFing the same hotel (which could happen if the site for every hotel was posted publicly) would just lead to the hotel shutting down the LNF opportunities faster.
I've already seen one hotel, at which I did multiple LNFs over a short period of time, withdraw itself completely from the third-party site I'd used! This would happen even more often if these sites were published for all to see on FT. (In part, because lots of things that are published on FT then go on to even more widely-read sites, such as travel blogs or even major newspapers and magazines!)